In the application of anesthetic or analgesic gases by means of a gas delivery mask to medical and dental patients, gas often escapes into the area around the patient's face and eventually dissipates into a wider area, exposing those in the vicinity to the gas. Studies of this problem are reported in Sass-Kortsak et al.: "Exposure of Hospital Operating Room Personnel to Potentially Harmful Environmental Agents". Am. Ind. Hyg. Assoc. J., Vol. 53, No. 3, March 1992, pp. 203-209 and Tran et al.: "Evaluation of Waste Anesthetic Gases Monitoring Strategies, and Correlations Between Nitrous Oxide Levels and Health Symptoms". Am. Ind. Hyg. Assoc. J., Vol. 55, No. 1, January 1994, pp. 37-41.
Various proposals have been made for dealing with this problem. These include auxiliary ventilation, as reported in Mickelsen et al.: "Auxiliary Ventilation for the Control of Nitrous Oxide in a Dental Clinic". Appl. Occp. Environ. Hyg., Vol 8, No. 6, June 1993, pp. 564-570. That study concluded that air flow rates sufficiently high to cause noise problems or a hood relatively close to the patient would be required for adequate control. Neither high noise levels nor a hood close to a patient's face is acceptable in many, if not most, dental and surgical applications. For example, in dentistry full access to the patient's mouth, without obstruction, is required.
Other proposals are found in the following:
U.S. Pat. No. 5,195,512 issued Mar. 23, 1993, which discloses a suction tube supported in position above the patient's face;
U.S. Pat. No. 4,807,617 issued Feb. 28, 1989, which discloses a mask with a scavenging cup on its outer side;
U.S. Pat. No. 3,877,691 issued Apr. 15, 1975, which discloses a hollow hood or shield, perforated on one side and connected to a suction line;
U.S. Pat. No. 4,895,172 issued Jan. 23, 1990, which discloses a hollow cup that is set over a patient's chin and attached to the patient's head with a harness. Gases are drawn into openings in the front of the cup and thence to a vacuum source.
None of these devices is fully satisfactory. Hoods, shields and masks cover the face at least partially and are not useful in many applications. Suction devices spaced from the face are not exceptionally effective as reported by Mickelsen et al. (supra). A suction arrangement at the chin will not adequately draw in gases leaking from a mask around the nose, because the mask, the hands of a dentist or other obstructions are in the flow path. A chin cup also obstructs access to the mouth for dental and the like treatments.
The present invention is concerned with a method and an apparatus for the effective capturing of these medical gases, and fumes, mists and particulates generated during dental and surgical procedures, while allowing substantially full access to the patient's face, including mouth and nose, for dental treatment, the administration of the gases or substantially any other purpose desired.